JP7547935B2 - Coil and manufacturing method thereof, power transmission device, power receiving device, and power transmission system - Google Patents

Description

The present invention belongs to the technical fields of coils and their manufacturing methods, power transmission devices, power receiving devices, and power transmission systems, and more specifically, to the technical fields of coils for contactless power transmission and their manufacturing methods, and contactless power transmission devices, power receiving devices, and power transmission systems that use the coils.

In recent years, electric vehicles equipped with storage batteries such as lithium-ion batteries are becoming more common. In such electric vehicles, the motor is driven by the power stored in the storage battery to move, so efficient charging of the storage battery is required. Therefore, as a method for charging the storage battery mounted on the electric vehicle without physically connecting a charging plug or the like to the electric vehicle, research has been conducted on so-called wireless power transmission, which uses a receiving coil and a transmitting coil that are separated and opposed from each other. Wireless power transmission methods generally include an electric field coupling method, an electromagnetic induction method, and a magnetic field resonance method. When these methods are compared from the viewpoints of, for example, the frequency of the power transmitted and received, the degree of freedom in the horizontal and vertical directions, and the transmission efficiency, the electric field coupling method using a capacitor or the magnetic field resonance method using a coil is considered to be promising as a wireless power transmission method for charging the storage battery mounted on the electric vehicle, and research and development into these methods is also being actively conducted. For example, the following Patent Document 1 can be cited as a prior art document disclosing such background technology. This patent document 1 discloses a coil that transmits power by magnetic resonance using a loop coil with one winding (1 turn) and an open coil with 5.5 windings (5.5 turns).

JP 2011-200045 A

On the other hand, the above-mentioned wireless power transmission (contactless power supply) for electric vehicles requires the transmission (i.e., flowing through the coil) of a high-output power of at least 3.7 kilowatts. Therefore, if the resistance of the conductor (coil) increases as a result of passing such high-output power (current), Joule heat will be generated, resulting in large losses in the coil and reducing the efficiency of wireless power transmission.

As a method for reducing the resistance caused by the loss in the coil, it is considered to construct the coil itself using twisted wire (so-called Litz wire). However, when considering that the receiving coil will be installed in a private vehicle, constructing the coil using the twisted wire leads to an increase in the weight and price of the coil. A conventional technique for solving this problem is to manufacture a coil by patterning and etching a core material made of, for example, thin copper films and insulating layers that insulate the thin films into the shape of the coil using a so-called photolithography method.

However, copper is generally expensive, and its reserves as a resource are not abundant. In contrast, materials that are used as conductive materials like copper include aluminum. Generally, aluminum is cheaper than copper, and its reserves are abundant. Aluminum also has a lower density than copper, which allows for weight reduction and cost reduction, and is thought to have many advantages when used in the above-mentioned private cars, etc.

However, aluminum has a conductivity that is about one-third that of copper (meaning that the resistance and corresponding losses are large), and there are problems with soldering cables for inputting and outputting power to and from the power source.

The present invention has been made in consideration of the above problems and demands, and one example of the objective is to provide a coil and a manufacturing method thereof that can reduce the cost and weight of a coil for wireless power transmission, improve the transmission efficiency of the coil, and prevent an increase in operating temperature, as well as a non-contact power transmission device, power receiving device, and power transmission system that use the coil.

In order to solve the above problems, the invention described in claim 1 provides a coil for use in contactless power transmission, comprising a winding wound in a winding direction of the coil, the winding consisting of a metallic core material extending in the winding direction and a metallic coating material that covers at least a portion of a surface of the core material along the winding direction, wherein the density of the core material is lower than the density of the coating material, the conductivity of the coating material is higher than the conductivity of the core material, and the thickness of the coating material is less than half the skin depth at which a skin effect appears at the frequency of the current used for the power transmission .

According to the invention described in claim 1, the winding wire wound in the winding direction is made of a metallic core material and a coating material, and since the density of the core material is lower than that of the coating material and the conductivity of the coating material is higher than that of the core material, the conductivity of the portion close to the surface of the winding wire is high, while the density of the core material close to the center of the winding wire is lower than that of the coating material, so that it is possible to simultaneously improve the transmission efficiency by reducing the loss of the coil and prevent the operating temperature from increasing, as well as to reduce the weight and cost of the coil. In addition, since the thickness of the coating material is less than half the skin depth at which the skin effect appears at the frequency of the current used for power transmission, it is possible to effectively reduce the AC resistance caused by the skin effect generated in the coil due to power transmission.

In order to solve the above problem, the invention described in claim 2 is the coil described in claim 1, in which the shape of the cross section perpendicular to the central axis of the core material is a rectangle having long sides parallel to the winding surface of the winding wire in the coil, and the coating material covers at least one of the long sides along the winding direction.

According to the invention described in claim 2, in addition to the effect of the invention described in claim 1, the cross section perpendicular to the central axis of the core material is a rectangle having long sides parallel to the winding surface of the winding wire in the coil, and the coating material covers at least one of the long sides along the winding direction, which promotes weight reduction and cost reduction of the coil.

To solve the above problem, the invention described in claim 3 is the coil described in claim 2, in which the coating material coats the two long sides along the winding direction.

According to the invention described in claim 3, in addition to the effect of the invention described in claim 2, the two long sides in the cross section of the core material are covered with the covering material along the winding direction, which can promote loss reduction.

To solve the above problem, the invention described in claim 4 is the coil described in claim 2 or claim 3, in which the coating material covers the entire surface of the core material.

According to the invention described in claim 4, in addition to the effects of the invention described in claim 2 or 3, the coating material covers the entire surface of the core material, which can further promote loss reduction.

In order to solve the above problem, the invention described in claim 5 is a coil described in any one of claims 1 to 4 , wherein the core material is an aluminum core material and the coating material is a copper coating material.

According to the invention described in claim 5 , in addition to the effect of the invention described in any one of claims 1 to 4 , since the core material is made of aluminum and the coating material is made of copper, it is possible to effectively achieve both improved transmission efficiency and prevention of increases in operating temperature, as well as reduced weight and cost of the coil.

In order to solve the above problem, the invention described in claim 6 provides a power transmission system including a power transmission device and a power receiving device spaced apart from the power transmission device, and which transmits power from the power transmission device to the power receiving device in a non-contact manner, the power transmission device comprising a power transmission coil which is the coil described in any one of claims 1 to 5 , the power transmission coil being arranged opposite the power receiving device, and an output means which outputs the power to be transmitted to the power transmission coil.

In order to solve the above problem, the invention described in claim 7 is a power receiving device included in a power transmission system composed of a power transmitting device and a power receiving device separated from the power transmitting device, and which transmits power from the power transmitting device to the power receiving device in a non-contact manner, the power receiving device comprising a power receiving coil which is the coil described in any one of claims 1 to 5 , the power receiving coil being arranged opposite the power transmitting device, and an input means connected to the power receiving coil.

In order to solve the above problem, the invention described in claim 8 comprises a power transmission device described in claim 6 , and a power receiving device that is spaced apart from the power transmission device and faces the power transmission coil, and receives power transmitted from the power transmission device.

In order to solve the above problem, the invention described in claim 9 comprises a power transmitting device and a power receiving device described in claim 7 , which is positioned away from the power transmitting device and has the power receiving coil facing the power transmitting device, and receives power transmitted from the power transmitting device.
A non-contact power transmission system.

According to the invention described in any one of claims 6 to 9 , at least one of the power transmitting coil provided in the power transmitting device or the power receiving coil provided in the power receiving device constituting the power transmission system is the coil described in any one of claims 1 to 5 , so that when the power transmitting coil or the power receiving coil is placed opposite each other to perform non-contact power transmission, it is possible to achieve both improved transmission efficiency due to the reduction in loss and prevention of an increase in operating temperature, as well as reduced weight and cost of the coil. In addition, since the thickness of the covering material is equal to or less than half the skin depth at which the skin effect appears at the frequency of the current used for power transmission, it is possible to effectively reduce the AC resistance caused by the skin effect generated in the coil due to power transmission.

In order to solve the above problems, the invention described in claim 10 is a method for manufacturing a coil described in any one of claims 1 to 5 , comprising a core material manufacturing process for manufacturing the core material by punching a metal plate that becomes the core material, and a coating material forming process for forming the coating material by an electroplating method on the portion of the manufactured core material to be covered, wherein in the coating material forming process, the coating material is formed so that the thickness of the coating material is less than half the skin depth at which the skin effect appears at the frequency of the current used for the power transmission .

According to the invention as set forth in claim 10 , since the method includes a core material manufacturing step and a coating material forming step, the coil as set forth in any one of claims 1 to 5 can be efficiently manufactured.

According to the present invention, the winding wire wound in the winding direction is made of a metal core material and a coating material, the density of the core material is lower than the density of the coating material, and the conductivity of the coating material is higher than the conductivity of the core material.

Therefore, while the electrical conductivity is high near the surface of the winding, the density of the core material near the center of the winding is lower than the density of the coating material, so that it is possible to improve transmission efficiency by reducing loss in the coil and prevent an increase in operating temperature, while also achieving a lightweight and low-cost coil. Also, because the thickness of the coating material is less than half the skin depth at which the skin effect appears at the frequency of the current used in power transmission, it is possible to effectively reduce the AC resistance caused by the skin effect that occurs in the coil due to power transmission.

1 is a block diagram showing a schematic configuration of a power transmission system according to an embodiment; FIG. 2 is a plan view illustrating a structure of a power transmission coil according to an embodiment. 1A is a cross-sectional view showing the structure of a power transmission coil of an embodiment, (a) is a cross-sectional view showing the structure of the power transmission coil, (b) is a cross-sectional view showing the structure of a power transmission coil of a first modified form, (c) is a cross-sectional view showing the structure of a power transmission coil of a second modified form, and (d) is a cross-sectional view showing the structure of a power transmission coil of a third modified form. 4 is a flowchart showing a method for manufacturing a power transmission coil according to an embodiment. 1 is a graph showing the relationship between the overall thickness of the copper thin film wire and the Q value as an effect of the structures of the power transmitting coil and the power receiving coil of the embodiment. FIG.

Next, a description will be given of an embodiment of the present invention with reference to Figs. 1 to 3. The embodiment and modified embodiment described below are embodiments and modified embodiments in which the present invention is applied to a power transmission system that transmits power for charging a rechargeable battery mounted on an electric vehicle to the electric vehicle equipped with the rechargeable battery in a non-contact manner using magnetic resonance.

Here, the magnetic field resonance type power transmission system of the embodiment and modified form includes a power transmission coil (described below) that transmits power, and a power receiving coil (described below) that is disposed facing (i.e., opposite) the power transmission coil at a distance from the power transmission coil and receives the power transmitted from the power transmission coil.

(I) Overall configuration and operation of the power transmission system according to the embodiment
First, the overall configuration and operation of a power transmission system according to an embodiment will be described with reference to Fig. 1. Fig. 1 is a block diagram showing a schematic configuration of a power transmission system according to an embodiment.

As shown in FIG. 1, the power transmission system S of the embodiment is composed of a power receiving device R having a power receiving unit RV and the above-mentioned power receiving coil RC, and a power transmitting device T having a power transmitting unit TR and the above-mentioned power transmitting coil TC. At this time, the power receiving device R is mounted on the electric vehicle and is connected to a storage battery (not shown) mounted on the electric vehicle. On the other hand, the power transmitting device T is installed on the ground at a position where the electric vehicle moves or stops. When charging the storage battery, the electric vehicle is driven or stopped so that the power receiving coil RC of the power receiving device R and the power transmitting coil TC of the power transmitting device T face each other. Note that when charging the storage battery by the power transmission system S of the embodiment, it can be configured to transmit power from the power transmitting device T to the power receiving device R mounted on the stopped electric vehicle via the power transmitting coil TC of the power transmitting device T installed on the ground below the stopping position. Alternatively, the power receiving device R mounted on a moving electric vehicle may be configured to continuously transmit power from the power transmitting device T via the power transmitting coils TC of multiple power transmitting devices T installed in a section of a certain distance on the road on which the electric vehicle is traveling. In this case, the power transmitting unit TR corresponds to an example of the "output means" of the present invention, and the power receiving unit RV corresponds to an example of the "input means" of the present invention.

Meanwhile, the power to be transmitted to the power receiving device R is input from the power transmitting unit TR to the power transmitting coil TC. As a result, the power transmitting coil TC transmits the power to the power receiving coil RC by the magnetic field resonance method. At this time, the power transmitting coil TC and the power receiving coil RC each correspond to an example of a "coil" in the present invention.

In the above configuration, the power transmission unit TR of the power transmission device T outputs the power to be transmitted to the power receiving device R to the power transmission coil TC while complying with laws and regulations such as the Radio Act in the country in which the power transmission system S is used. As a result, the power transmission coil TC transmits the output power to the power receiving coil RC by a magnetic field resonance method. The laws and regulations to be complied with at this time regulate the leakage magnetic field to be below a predetermined level, taking into account the effects on the human body. In addition, in order to enable interconnection between all the power transmission devices T and the power receiving devices R, it is necessary for both to use a predetermined range of frequencies, and therefore the predetermined range of frequencies or frequency bands must follow the recommendations of international organizations such as ISO (International Organization for Standardization) or IEC (International Electrotechnical Commission) as the laws and regulations. In addition, the lower limit of the transmission efficiency taking into account a predetermined positional deviation between the power transmission coil TC and the power receiving coil RC is also specified by the international organization, so that the power transmission system S is also required to have a high power transmission efficiency.

The receiving coil RC of the power receiving device R, which receives the power from the power transmitting coil TC by the magnetic field resonance method, outputs the received power to the power receiving unit RV. As a result, the power receiving unit RV converts the output corresponding to the power (for example, high-frequency power of 85 kHz as described below) into a DC (direct current) current, for example, by a power conversion unit (not shown), and outputs it to the storage battery of the electric vehicle. With the above configuration of the power receiving device R, the storage battery is charged with the required amount of power.

(II) Configuration of the transmitting coil TC (receiving coil RC)
Next, the configuration of the power transmitting coil TC and the power receiving coil RC of the embodiment used in the power transmission system S of the above-mentioned embodiment will be described with reference to FIG. 2. The power transmitting coil TC and the power receiving coil RC of the embodiment basically have the same configuration. Therefore, in the following description, the structure of the power transmitting coil TC will be described. FIG. 2 is a plan view showing the structure of the power transmitting coil TC of the embodiment, and is a plan view of the power transmitting coil TC as viewed from the power receiving device R side in the power transmitting device T (see FIG. 1).

As shown in the plan view of FIG. 2, the power transmission coil TC of the embodiment is configured by stacking two parallel-wound copper thin-film wires, for example, copper thin-film wire TL1 and copper thin-film wire TL2, on an insulating film BF (described in detail later). In this configuration, each of the copper thin-film wire TL1 and copper thin-film wire TL2 corresponds to an example of a "winding line" of the present invention. In this embodiment, the film BF is used to stack the power transmission coil TC, but other insulating materials such as glass epoxy materials can also be used. In addition, in order to efficiently dissipate heat generated by the power transmission coil TC, a thin-film material in which ceramic particles are dispersed, for example, can also be used. Furthermore, the centers of winding of the copper thin-film wire TL1 and the copper thin-film wire TL2 are the same or approximately the same in each winding.

2, the power transmission coil TC is composed of the copper thin film wire TL1 and the copper thin film wire TL2 wound in parallel to each other in the same layer, and has an external connection terminal O1 and an external connection terminal O2 on one side of the outermost circumference to connect the copper thin film wire TL1 and the copper thin film wire TL2 and to connect the copper thin film wire TL1 and the copper thin film wire TL2 to the power transmission unit TR. The power transmission coil TC is composed of the parallel copper thin film wire TL1 and the copper thin film wire TL2 wound counterclockwise four times (four turns) from the position of the external connection terminal O1 (the right side in the case shown in FIG. 2), and the other end of each of the copper thin film wire TL1 and the copper thin film wire TL2 is drawn from the innermost circumference to the outermost circumference (the right side in the case shown in FIG. 2) in the winding, and is formed as the external connection terminal O2. At the intersections of the copper thin film wires TL1 and TL2 (intersections shown by dashed lines in the lower right of FIG. 2), the copper thin film wires TL1 and TL2 are insulated from each other and cross each other by a laminated structure sandwiching a film BF or other insulating layer, or by a method using a jumper wire, etc. In addition, the copper thin film wires TL1 and TL2 in the example shown in FIG. 2 each have the same width and thickness over the entire circumference. Furthermore, the copper thin film wires TL1 and TL2 each have straight line portions on the upper, lower, left and right sides in FIG. 2, and the straight line portions are connected by curved portions of approximately concentric arcs. In the embodiment of the power transmission coil TC, the relationship between the width W1 of the copper thin film wire TL1 and the width W2 of the copper thin film wire TL2 shown in FIG. 2 is such that the width W1 is smaller than the width W2 throughout the power transmission coil TC, thereby reducing the AC resistance in the power transmission coil TC or the power receiving coil RC, as described below.

Next, the structure of each of the copper thin film wires TL1 and TL2 will be described with reference to FIG. 3, along with the structures of the related copper thin film wires of the first and second modified forms. FIG. 3 is a cross-sectional view showing the structure of the power transmission coil TC of the embodiment.

First, the structures of the copper thin film wire TL1 and the copper thin film wire TL2 constituting the power transmission coil TC of the embodiment will be described with reference to FIG. 3(a), with the copper thin film wire TL2 as a representative. The cross-sectional structure of the copper thin film wire TL1 is the same as the cross-sectional structure of the copper thin film wire TL2, except for its width W1.

Here, the frequency of the power transmitted from the power transmission coil TC to the power receiving coil RC by the power transmission system S of the embodiment is predetermined, for example, by law. More specifically, in the case of power transmission by the power transmission system S of the embodiment (i.e., power transmission to the electric vehicle), the frequency is set to a high frequency of 85 kHz. At this time, it is known that when a high-frequency current flows through a conductor, the current density is high on the surface of the conductor and decreases from the surface toward the center. In addition, in this regard, the higher the frequency of the current, the more the current is concentrated on the surface, and as a result, the AC resistance of the conductor increases. This phenomenon is known as the so-called "skin effect of the conductor". In the following description, the AC resistance of the conductor when a high-frequency current flows through the conductor is simply referred to as "impedance". Furthermore, in the power transmission by the power transmission system S of the embodiment, if an attempt is made to transmit high-output power using the high-frequency current of 85 kHz, the resistance of the copper thin-film wire TL1 and the copper thin-film wire TL2 will become even higher due to the skin effect as a result of passing the high-output power (current), and the loss due to Joule heat will increase, which will also reduce the efficiency of the power transmission.

Another electrical phenomenon that reduces the efficiency of wireless power transmission using high frequencies, similar to the skin effect, is the so-called "conductor proximity effect," which occurs when the copper thin-film wires TL1 or TL2 are in close proximity to each other in each winding. Therefore, measures must be taken to prevent the increase in impedance caused by this proximity effect.

Therefore, the copper thin film wire TL2 constituting the power transmission coil TC of the embodiment is configured by laminating, in order from the film BF side, a copper thin film 2 as a coating material, an aluminum thin film 10 as a core material, and a copper thin film 1 as a coating material, as shown in the cross-sectional view of FIG. 3(a) over the entire circumference of the power transmission coil TC. That is, in the copper thin film wire TL2, the surface (both front and back sides) of the copper thin film wire TL2, where the increase in impedance due to the skin effect or the proximity effect is generally considered to be large, is formed of copper thin film 1 and copper thin film 2 (i.e., copper thin film 1 and copper thin film 2 having a higher conductivity than the aluminum thin film 10), thereby suppressing the increase in impedance. In addition, in the copper thin film wire TL2, the part near the center of the copper thin film wire TL2, where the increase in impedance due to the skin effect or the proximity effect is considered to be small, is formed of aluminum thin film 10 (i.e., aluminum thin film 10 having a lower density than the copper thin film 1 and copper thin film 2), thereby reducing the weight and cost of the copper thin film wire TL2 (i.e., the power transmission coil TC). At this time, the thickness of each of the copper thin film 1 and the copper thin film 2 is, for example, 25 micrometers, which is less than half the thickness of the skin part on the surface of the copper thin film wire TL2 where the skin effect and the proximity effect appear. In contrast, the thickness of the aluminum thin film 10 is, for example, 500 micrometers. The copper thin film wire TL2 is then bonded, for example, to the film BF on the surface of the copper thin film 2 to form the transmission coil TC.

Note that multiple modified cross-sectional structures can be adopted for the copper thin film wire TL1 and copper thin film wire TL2 of the embodiment, and these modified cross-sectional structures are described using Figs. 3(b) to 3(d) with the copper thin film wire corresponding to copper thin film wire TL2 as a representative. Note that the cross-sectional structure of each modified copper thin film wire corresponding to copper thin film wire TL1 is the same as the cross-sectional structure of each modified copper thin film wire corresponding to copper thin film wire TL2, except for its width. Also, in Figs. 3(b) to 3(d), the same steel members as those in the power transmission coil TC of the embodiment are given the same member numbers and detailed descriptions are omitted.

That is, as the first modified form, as shown in the cross section of FIG. 3(b), the copper thin film wire TL2a of the first modified form is configured by laminating an aluminum thin film 10 and a copper thin film 3 in this order from the film BF side all around the circumference of the power transmission coil of the first modified form. The copper thin film 3 has a thickness of, for example, 100 micrometers, and the aluminum thin film 10 has a thickness of, for example, 500 micrometers, similar to the copper thin film wire TL2 of the embodiment. In this case, the copper thin film wire TL2a of the first modified form has the copper thin film 3 laminated only on one side of the copper thin film wire TL2a, which is susceptible to the above-mentioned skin effect and the above-mentioned proximity effect. The copper thin film wire TL2a is then, for example, bonded to the film BF on the surface of the aluminum thin film 10, thereby forming the power transmission coil of the first modified form.

As a second modified form, as shown in FIG. 3(c), the copper thin film wire TL2b of the second modified form is constructed by laminating a copper thin film 4, an aluminum thin film 10, and a copper thin film 3 in this order from the film BF side over the entire circumference of the power transmission coil of the second modified form. The copper thin film 3 and the copper thin film 4 each have a thickness of, for example, 100 micrometers, and the aluminum thin film 10 has a thickness of, for example, 500 micrometers. In this case, the copper thin film wire TL2b of the second modified form has a copper thin film 3 and a copper thin film 4 of different thicknesses from the copper thin film wire TL2 of the embodiment laminated on two sides of the copper thin film wire TL2a, which is susceptible to the skin effect and the proximity effect, like the copper thin film wire TL2 of the embodiment. The copper thin film wire TL2b is bonded, for example, to the film BF on the side of the copper thin film 4 to construct the power transmission coil of the second modified form.

Finally, as a third modified form, as shown in the cross section of FIG. 3(d), the copper thin film wire TL2c of the third modified form has the entire periphery of the aluminum thin film 10 covered with the copper thin film 5 over the entire circumference of the power transmission coil of the third modified form, and the aluminum thin film 10 and the copper thin film 5 in this state are bonded/laminated onto the film BF. The copper thin film 5 has a thickness of, for example, 100 micrometers, and the aluminum thin film 10 has a thickness of, for example, 500 micrometers.

(III) Manufacturing method of the power transmission coil TC (power receiving coil RC)
Next, an outline of a method for manufacturing the power transmission coil TC according to the embodiment will be described with reference to Fig. 4. The manufacturing method described below can also be used as a method for manufacturing a power receiving coil RC having a similar configuration to the power transmission coil TC. Fig. 4 is a flowchart showing the method for manufacturing the power transmission coil according to the embodiment.

More specifically, the method for manufacturing the transmission coil TC can include the following steps (a) to (d).

(a) An aluminum thin film material having the same thickness as the aluminum thin film 10 (e.g., 500 micrometers) is punched out, for example, by a punching method, to produce an aluminum thin film 10 corresponding to the core material of each of the copper thin film wires TL1 and TL2 (step S1). Note that this step S1 is similar when producing each of the copper thin film wires TL2a of the first modified form to the copper thin film wires TL2c of the third modified form.

(b) The copper thin film 1 and copper thin film 2 are formed to the required thickness (e.g., 25 micrometers) by, for example, electroplating on the upper and lower surfaces in FIG. 3(a) of the aluminum thin film 10 produced in step S1 (step S2). In the step S2 when producing the copper thin film wire TL2a of the first modified form, the copper thin film 3 is formed to a thickness of, for example, 100 micrometers only on the upper surface of the aluminum thin film 10 in FIG. 3(b). In the step S2 when producing the copper thin film wire TL2b of the second modified form, the copper thin film 3 and copper thin film 4 are formed to a thickness of, for example, 100 micrometers on the upper and lower surfaces in FIG. 3(c) of the aluminum thin film 10. In addition, in the step S2 when producing the copper thin film wire TL2c of the third modified form, the copper thin film 5 is formed to the required thickness on the entire peripheral surface of the aluminum thin film 10.

(c) The copper thin film wire TL2 manufactured in (b) above is, for example, glued to a corresponding position on the film BF to form the transmission coil TC of the embodiment (step S3).

(d) Connect the external connection terminals O1 and O2 of the power transmission coil TC manufactured in (c) above to the power transmission unit TR (step S4).

Next, as an effect of the structure of the power transmission coil TC and the power receiving coil RC including the copper thin film wire TL1 and the copper thin film wire TL2 of the embodiment having the structure shown in Figures 2 and 3(a), the relationship between the overall thickness of each of the copper thin film wire TL1 and the copper thin film wire TL2 and the Q value in power transmission by the power transmission system S of the embodiment including the power transmission coil TC and the power receiving coil RC will be described using Figure 5 and the following Table 1. Note that Figure 5 is a graph showing the relationship between the overall thickness of the copper thin film wire and the Q value as an effect of the structure of the power transmission coil TC and the power receiving coil RC of the embodiment. Here, Fig. 5 shows experimental results (simulation results) of measuring the relationship between the overall thickness of each of the copper thin film wire TL2, the copper thin film wire TL2a, and the copper thin film wire TL2b and the above-mentioned Q value in power transmission using each power transmission coil for each of the power transmission coil TC and the power receiving coil RC of the embodiment having the structure (cross-sectional structure) shown in Fig. 2 and Fig. 3(a), the power transmission coil and the power receiving coil of the first modified form having the structure (cross-sectional structure) shown in Fig. 3(b), and the power transmission coil and the power receiving coil of the second modified form having the structure (cross-sectional structure) shown in Fig. 3(c). In comparison with these, Fig. 5 also shows the Q value in power transmission using a power transmission coil and a power transmission coil having a conventional structure.

5 shows the results of the experiment, the conventional copper thin film wires are a conventional copper thin film wire made of only a copper thin film and a conventional copper thin film wire made of only an aluminum thin film. The width of each of the copper thin film wires is set to the same width W2 as the copper thin film wire TL2 of the embodiment, and the thicknesses of each are shown in Table 1 below.

As shown in FIG. 5 and Table 1, compared to the transmitting coil and receiving coil having the conventional structure, the copper thin film wire TL2, etc. of the embodiment and the first and second modified forms are lighter as a transmitting coil and receiving coil, while achieving a Q value equivalent to that of the conventional example consisting of only copper thin film wire. Furthermore, since the copper thin film wire TL2, etc. of the embodiment and the first and second modified forms have a copper surface, the problem of low conductivity when the above-mentioned skin effect and the above-mentioned proximity effect are taken into account, and the problem of connectivity of the input/output cable is also solved.

As described above, according to the structure of the power transmission coil TC and the power receiving coil RC of the embodiment, the copper thin film wire TL1 and the copper thin film wire TL2 wound in the respective winding directions are composed of an aluminum thin film 10 as a core material and a copper thin film 1 and a copper thin film 2 as a coating material, and the density of the aluminum thin film 10 is lower than the density of the copper thin film 1 and the copper thin film 2, and the conductivity of the copper thin film 1 and the copper thin film 2 is higher than the conductivity of the aluminum thin film 10, so that the conductivity of the copper thin film wire TL1 and the copper thin film wire TL2 near the surface is high, while the density of the core material near the center of the copper thin film wire TL1 and the copper thin film wire TL2 is lower than the density of the coating material, so that it is possible to achieve both improved transmission efficiency and prevention of an increase in operating temperature due to a reduction in impedance caused by the so-called skin effect or proximity effect, as well as weight reduction and cost reduction of the coil.

In addition, the cross section perpendicular to the central axis of the copper thin film wire TL1 and the copper thin film wire TL2 of the aluminum thin film 10 as the core material is a rectangle with long sides parallel to the winding surface, and the copper thin film 1 or the like as the coating material coats at least one of the long sides along the winding direction (see Figure 3), which promotes weight reduction and cost reduction of the power transmission coil TC and the power receiving coil RC.

Furthermore, in the case of the copper thin film wire TL2 of the embodiment and the copper thin film wire TL2b of the second modified embodiment, the two long sides in the cross section of the core material are covered with the coating material along the winding direction, which can promote a reduction in impedance.

Furthermore, in the case of the third modified copper thin film wire TL2c, the copper thin film 5 as the coating material is coated all around the aluminum thin film 10 as the core material, which can further promote reduction in impedance.

Furthermore, the thickness of the copper thin film 1 or the like used as the coating material is less than half the skin depth (i.e., 25 micrometers to 100 micrometers) at which the skin effect appears at the frequency of the current used in power transmission by the power transmission system S of the embodiment (i.e., 85 kilohertz), so that the impedance due to the power transmission can be effectively reduced.

Furthermore, since the core material is an aluminum thin film 10 and the coating material is a copper thin film 1 or the like, it is possible to effectively achieve both improved transmission efficiency and prevention of increases in operating temperature, as well as reduced weight and cost for the transmitting coil TC and the receiving coil RC.

As explained above, the present invention can be used in the field of contactless power transmission, and particularly when applied to the field of power transmission for charging storage batteries installed in electric vehicles, it can produce particularly remarkable effects.

1, 2, 3, 4, 5 Copper thin film 10 Aluminum thin film S Power transmission system R Power receiving device RV Power receiving section RC Power transmitting coil T Power transmitting device TR Power transmitting section TC Power transmitting coil TL1, TL2, TL2a, TL2b, TL2c Copper thin film wire BF film O1, O2 External connection terminal

Claims (10)

In a coil used for contactless power transmission,
A winding wire wound in a winding direction of the coil,
A metal core extending in the winding direction;
a metal covering material that covers at least a portion of the surface of the core material along the winding direction;
A winding comprising:
the density of the core material is lower than the density of the covering material,
the electrical conductivity of the coating material is higher than the electrical conductivity of the core material,
A coil characterized in that the thickness of the coating material is less than half the skin depth at which the skin effect appears at the frequency of the current used for the power transmission . 2. The coil according to claim 1,
a cross-sectional shape perpendicular to a central axis of the core material is a rectangle having a long side parallel to a winding plane of the winding wire in the coil,
A coil characterized in that the covering material covers at least one of the long sides along the winding direction. The coil according to claim 2,
A coil characterized in that the covering material covers the two long sides along the winding direction. The coil according to claim 2 or 3,
A coil, characterized in that the coating material covers the entire surface of the core material. The coil according to any one of claims 1 to 4,
The core material is an aluminum core material,
A coil characterized in that the coating material is made of copper . A power transmission system includes a power transmission device and a power receiving device separated from the power transmission device, and transmits power from the power transmission device to the power receiving device in a non-contact manner.
6. The coil according to claim 1 , wherein the coil is a power transmitting coil arranged to face the power receiving device;
an output means for outputting power to be transmitted to the power transmitting coil;
A power transmitting device comprising : A power transmission system includes a power transmission device and a power receiving device that is separated from the power transmission device, and the power receiving device transmits power from the power transmission device to the power receiving device in a non-contact manner.
A power receiving coil according to any one of claims 1 to 5 , the power receiving coil being disposed opposite the power transmitting device;
An input means connected to the receiving coil;
A power receiving device comprising: The power transmitting device according to claim 6 ;
a power receiving device disposed away from the power transmitting device and facing the power transmitting coil, the power receiving device receiving the power transmitted from the power transmitting device;
A non-contact power transmission system comprising : A power transmission device;
8. The power receiving device according to claim 7 , wherein the power receiving coil is disposed opposite the power transmitting device and away from the power transmitting device, and the power receiving device receives power transmitted from the power transmitting device;
A non-contact power transmission system comprising: A method for manufacturing the coil according to any one of claims 1 to 5, comprising the steps of:
a core material manufacturing step of manufacturing the core material by punching a metal plate to be the core material;
a coating material forming step of forming the coating material on the portion of the manufactured core material to be coated by an electroplating method;
Including,
A method for manufacturing a coil, characterized in that in the coating material formation step, the coating material is formed so that the thickness of the coating material is less than half the skin depth at which the skin effect appears at the frequency of the current used for the power transmission .

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